A great part of medical research is based on collecting numerous blood samples from patients and healthy test persons. This necessitates insertion of sampling and infusion cannulas in peripheral arm veins. Tolerance tests are also carried out in routine medical services and form the basis of many endocrine analyses. Also our entire hormone diagnostics is based on venipuncture. Since not all patients have vessels perfect to puncture, it has been necessary to employ specialized test nurses well trained in puncturing and managing the insertion of test needles in a patient. Many patients with endocrine diseases have bad vessels. Such diseases are, e.g., Cushing's syndrome, Addison's disease, diabetes, hypofysial malfunctions such as obesity, and so on. It has become routine therefore, to utilize commonly available heat pads for heating of an arm before a puncturing attempt is made. In this way the circulation is increased and a better filling of the vessels is obtained, which facilitates cannula insertion. The existing heat pads, however, are not adapted to this purpose. They easily slip off and the heating efficiency is bad. For certain purposes these heat pads are quite unsuitable, e.g., when there is a need for arterialization of venous blood. The thermostat used in the pads periodically switches the current off; this results in great temperature fluctuations and consequently unpredictable variations in the arterialization of the blood.
There is a need, thus, for a suiatable thermal vascular dilator having a stable temperature steplessly variable between 27.degree. C. and 50.degree. C. Such a device would be useful in all instances of public medical care involving blood sampling as well as in polyclinical and institutional medical care. A vessel dilator would be a great help for all nurses who often have to make venipunctures on patients having bad vessels. It is commonly known in medical circles that this is a frequent problem. An efficient remedy should save much time and thereby release resources needed in other areas of the medical service.
It would be particularly valuable if all acute surgeries and intensive care surgeries could be equipped with several vascular dilators. It could then be possible to decrease the number of exposals and decrease the use of nurse anaesthetists for cannula and catheter insertions in sick patients. By using "arterialized" blood (i.e., increased circulation due to heat, whereby a greater part of artery blood enters the vein vessel system), it is not necessary in certain cases to utilize artery punction, but it is possible to take samples from a peripheral vein. Artery punction is often associated with a greater risk for the patient than ordinary venipunction.
Thus, a thermal vascular dilator can be used in numerous ways in both practical medical care and research. It has its place at all levels of medical care and in specialities, not least in children's hospitals and psychiatric clinics where venipuncture presents special problems.